https://orcid.org/0000-0001-5803-0008
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ABSTRACT
The Alpine–Himalayan collision zone involves a number of crustal fragments that originated in the Neoproterozoic to Cambrian Avalonian–Cadomian belt of northern Gondwana. We use the detrital zircon U–Pb geochronology to examine four of these lithotectonic units, now exposed in the Balkans in Bulgaria and Serbia. The obtained age spectra suggest that the Diabase–Phyllitoid Complex (the maximum depositional age, MDA, estimated at 540 + 5/-9 Ma) was presumably an accretionary wedge or a forearc basin sourced from a nearby volcanic arc, however, its palaeo-position remains uncertain. The Vlasina Complex (MDA of 577 + 5/-6 Ma) was the most ʽwesterly’ terrane, adjacent to the Trans-Saharan belt, whereas the Sredna Gora and Stara Planina complexes (MDAs of 546 ± 7 Ma and 579 + 4/-5, respectively) were positioned next to the Saharan Metacraton and Arabian–Nubian shield. To put the Balkan terranes into a broad context, we statistically compare the detrital zircon ages in other terranes from the Eastern Alps to Iran with igneous and metamorphic U–Pb zircon ages from North African source areas. The statistical comparison is done through multi-dimensional scaling (MDS), a more rigorous method than a visual comparison of age spectra, to examine the degree of inter-sample similarity. This information is then transferred to a tentative palaeogeographic map showing position of each terrane with respect to its most likely source region. As a result, we define a ʽwesterly’ terrane assemblage, characterized by Mesoproterozoic ages and sourced from the West African craton and the Trans-Saharan belt and an ʽeasterly’ assemblage formed next to the Saharan Metacraton and the Arabian–Nubian shield. The present-day position of some of these terranes implies significant dextral strike-slip displacement, perhaps due to movement on the Pangea megashear during the Carboniferous and Permian.
Acknowledgments
We thank Aral Okay and an anonymous reviewer for their constructive comments that helped to improve the original manuscript as well as Gültekin Topuz, Hossein Azizi, Jean-Pierre Burg, and Robert J. Stern for careful editorial handling. R. Damian Nance is gratefully acknowledged for discussions and comments on an early version of the manuscript, František Veselovský is thanked for mineral separations, Václav Santolík for help with creating part of the database of zircon ages, and Mezzek Mavrud for enhancing our discussions in the field.
Supplementary material
Supplemental data for this article can be accessed here.
Notes
1. In the modern literature, terranes are fault-bounded allochtonous tectonostratigraphic units that travelled a considerable distance, sometimes thousands of kilometres, from the site of their origin and with respect to each other. Although this may not (and likely does not) apply to all the peri-Gondwanan basement units, this terminology has been widely used and is also adopted here for the sake of simplicity.
